To provide a reel lawn mower equipped with an openable and closable safety guard.

This reel-type lawn mower has a mobile structure and a ground traction member which is rotatably joined to the mobile structure. The ground traction member tracks and moves the mobile structure at a ground speed on the ground. A power unit is supported by the mobile structure and outputs driving force to the ground traction member. A bed knife is supported by the mobile structure and has a cutting edge cooperating with a lawn-mowing reel which is rotatably supported on the mobile structure. A collecting device is attachable to or detachable from the mobile structure and collects mowed grass. A flap unit is rotatably joined to the mobile structure and positioned in a close position in which the lawn-mowing reel is hidden and an open position in which the lawn-mowing reel is exposed. An operation system drives the flap unit into the close position, when the collecting device is detached from the mobile structure, and drives the flap unit into the open position, when the collecting device is attached to the mobile structure.